1. Field of the Invention
The present invention relates to copper precursor compositions and their synthesis, and to the use of such copper precursor compositions for the fabrication of microelectronic device structures, e.g., in the formation of copper-based interconnects in the manufacture of semiconductor integrated circuits, or in otherwise metallizing or forming copper-containing films on a substrate by metalorganic chemical vapor deposition (MOCVD) utilizing such precursor compositions.
2. Description of the Related Art
The process of fabricating semiconductor integrated circuits generally includes the formation of metal interconnect lines. Such metal interconnect lines often are formed from multiple conductive layers. For example, a thin conductive layer (termed a xe2x80x9cbarrier layerxe2x80x9d in this context) may be formed from a metal, a metal nitride or a metal silicide, with a thicker conductive layer of aluminum, copper or other metal deposited over the barrier layer.
Many semiconductor device manufacturers are adopting copper metallization for use in production of microelectronic chips. Copper interconnects offer chip manufacturers a number of advantages, including enhanced circuit speed, improved performance and reduced electro-migration effects. Any of the one or more metal layers (e.g., bulk layer and/or seed layer) of a semiconductor integrated circuit may be formed utilizing a copper-based film. Furthermore, low resistivity, low contact resistance, and reduced RC time delays make copper particularly desirable for use in the metallization of very large scale integration (VLSI) devices.
In order to prevent detrimental effects caused by the interaction of a copper layer with other portions of the integrated circuit, a barrier layer is typically utilized in conjunction with the copper layers. Any of a wide range of barrier materials may be utilized including materials comprising metals, metal nitrides or metal silicides. Exemplary barrier materials include titanium nitride, titanium suicide, tantalum nitride, tantalum silicide, tungsten nitride, tungsten silicide and silicon doped metal nitrides. After the formation of a barrier layer, the copper is deposited on the barrier layer. The initial copper deposition may function as an electrochemical or CVD seed layer, e.g., an adhesive, conducting seed layer, followed by electrochemical plating or CVD of copper, for instance to complete the thin-film interconnect. Alternatively, the copper deposition may be employed to fully deposit the desired amount of copper.
For practical applications, the copper CVD precursors for the metallization composition should remain stable at room temperature and should not decompose at the vaporization temperature (e.g., the temperature required to efficiently vaporize the precursor). Concurrently, however, the precursor must decompose at elevated temperature to form high-purity Cu films on the heated substrate surface. The satisfaction of these parameters requires a delicate balance because the difference between the vaporization temperature and the film growth temperature is typically quite small (xcx9c100xc2x0 C.).
A suitable thermal stability can be realized by using bi-dentate neutral Lewis base ligands such as an ene-one. In this manner, the combination of the two coordination sites can be xe2x80x9cfine-tuned.xe2x80x9d Further, chelating complexes usually exhibit better stability than monodentate complexes.
Chemical vapor deposition (CVD) of copper provides uniform coverage for the metallization. Liquid CVD precursors enable direct delivery or liquid injection of the precursors into a CVD vaporizer unit. The accurate and precise delivery rate can be obtained through volumetric metering to achieve reproducible CVD metallization during VLSI device manufacturing.
Currently only a few liquid copper precursors are commercially available. These include (hfac)Cu(MHY), (hfac)Cu(3-hexyne), (hfac)Cu(DMCOD) and (hfac)Cu(VTMS), wherein hfac=1,1,1,5,5,5-hexafluoroacetylacetonato, MHY=2-methyl-1-hexen-3-yne, DMCOD=dimethylcyclooctadiene, and VTMS=vinyltrimethylsilane. However, concerns have arisen regarding perfluoro-xcex2-diketonate ligands, such as hfac, because the fluorine can react on the substrate surface forming a thin interface layer of CuF2, leading to poor adhesion and high contact resistances of Cu films on the substrate. Copper CVD precursors with a reduction of fluorine-content or without fluorine are therefore highly desirable. The present invention provides new (xcex2-diketonate)CuL precursors (wherein L is a coordinating ligand in the (xcex2-diketonate)CuL complex) with reduced and/or eliminated fluorine content in the complexes having utility in CVD of Cu thin films.
Furthermore, to achieve a reproducible film growth process, liquid precursors are extremely desirable. To date, only a few (hfac)CuL complexes are liquids that satisfy the requirements for CVD precursors. An organic solution prepared from a solid precursor provides a significant opportunity to increase the precursor availability for various purposes. However, it is well known that the solutions of (hfac)CuL complexes display poor stability. For example, a 50% ether solution of (hfac)Cu(MHY) decomposes in a few days at room temperature while the neat precursor is stable for at least 6 months. Therefore, there is a clear need to continuously develop reliable liquid source materials (neat or in a thermally stable chemical solution) for the CVD of Cu thin films. The present invention provides new stable (hfac)CuL precursors compositions and solutions.
As previously noted, the use of various copper precursors in CVD reactors to create copper interconnects in semiconductor integrated circuits, for example, is well known. U.S. Pat. Nos. 5,085,731; 5,098,516; 5,144,049; and 5,322,712 provide examples; and the references cited in these patents provide additional examples of such precursors. New and useful compositions and processes for the production of copper that improve upon, or provide alternatives to, these known compositions are highly desirable.
Copper CVD processes that are suitable for the large-scale manufacture of integrated circuits are extremely valuable to the electronics industry. Towards these ends, Cu CVD is generally used for two purposes: (1) deposition of a conductive thin-film layer as a plating base (xe2x80x9cseedxe2x80x9d) for electroplating processes; and (2) full-fill deposition of copper interconnects, features and multi-level structures.
There is, therefore, a need in the art for new and improved copper precursors for metallization in the manufacture of integrated circuits and other microelectronic device structures, using techniques such as CVD, plasma-assisted CVD, etc. Further, improved vaporization can lead to greatly improved deposition processes.
It is accordingly an object of the present invention to provide new copper precursors and formulations.
It is another object of the invention to provide methods of forming copper in the manufacturing of integrated circuits and other microelectronic device structures.
It is a further object of the invention to provide metallization technology for forming interconnects and other integrated device structures that overcome the shortcomings and limitations of the prior art, namely robust manufacturing.
It is another object of the invention to provide a method of metallizing or forming copper-containing thin films on a substrate by metalorganic chemical vapor deposition (MOCVD) utilizing such novel copper precursors and solution compositions.
Other objects and advantages of the present invention will be more fully apparent from the ensuing disclosure and appended claims.
The present invention relates to copper source reagent compositions, and to methods of making, stabilizing and using the same.
In one broad aspect, the present invention relates to novel (xcex2-diketonate)CuL precursors with increased thermal stability, with reduced fluorine content (relative to various corresponding commercial copper source reagents) and having utility for chemical vapor deposition (CVD) of copper thin films (i.e., copper deposited at a thickness of less than about 1000 xcexcm), as well as to methods for making and using such precursors and compositions.
In another aspect, the present invention relates to methods of synthesizing (xcex2-diketonate)CuL complexes, comprised of reacting Cu2O with corresponding (xcex2-diketonate)H in the presence of the desired Lewis base ligands, L, yielding complexes with increased thermal stability and/or reduced fluorine content as compared to the existing commercial copper MOCVD precursors.
In another embodiment the present invention relates to partially fluorinated or nonfluorinated xcex2-diketonates, such as tfac and tfdac and thd.
In a specific aspect, the present invention provides a CVD process that uses the aforementioned copper precursors, that may alternatively be in the form of neat liquid, as well as solution compositions of solid and liquid precursors of such type, for copper metallization or for forming copper seed layers, e.g., by direct liquid injection and vaporization. Vaporization may be effected by heating, by acoustics, by ultrasound or by nebulization.
The present invention also relates to novel stable (hfac)CuL precursors and to stable solutions for chemical vapor deposition of copper-containing thin films.
Another aspect of the invention relates to a method of forming a plating base xe2x80x9cseedxe2x80x9d layer on a substrate for subsequent electroplating, comprising deposition on the substrate of a layer of copper-containing material by liquid delivery CVD using a liquid-phase copper precursor, that is thermally stable at liquid delivery process temperatures, to form the layer of copper-containing material as the electrically conductive plating base seed layer.
A still further aspect of the invention relates to a microelectronic device structure comprising a substrate having a chemical vapor deposited copper plating base seed layer on the substrate, wherein the copper plating base seed layer has been formed using a liquid-phase copper precursor that is thermally stable at liquid delivery temperatures (at which the precursor liquid is vaporized to form a corresponding precursor vapor), but which is readily decomposable at chemical vapor deposition condition temperatures, to yield a copper-containing film on the substrate with which the precursor vapor is contacted.
Another aspect of the invention relates to a method of full-fill copper metallization of a microelectronic device structure, comprising liquid delivery chemical vapor deposition of copper metallization on the microelectronic device structure.
In a further aspect, the invention relates to methods of synthesizing (xcex2-diketonate)CuL complexes by reacting Cu2O with the corresponding (xcex2-diketonate)H in the presence of Lewis base ligand(s), L, yielding complexes having increased thermal stability and/or reduced fluorine content as compared to the existing commercial copper precursors.
In a specific compositional aspect, the invention relates to a (xcex2-diketonate)CuL complex, selected from the group consisting of:

wherein
M is xc2xd, 1 or 2
Rxe2x80x2 and Rxe2x80x3 are the same or different and are independently selected from the group consisting of C1-C8 acyclic alkyl, aryl, fluoroaryl, C1-C8 fluoroalkyl, C3-C6 cycloalkyl, and C3-C6 fluorocycloalkyl; and
L is a neutral Lewis base ligand, selected from the group consisting of (i) alkenes, (ii) alkynes, (iii) silicon containing ligands, and (iv) sulfur, oxygen and/or nitrogen-containing organic ligands;
(b) precursors of Formula II: 
xe2x80x83wherein
R1, R2, R3 R4 and R5 may be the same or different and are independently selected from the group consisting of H, aryl, fluoroaryl, C1-C8 acyclic alkyl, C1-C8 fluoroalkyl, or C3-C6 cycloalkyl, and
n is 0, 1, 2, or 3. The bonding mode can be intermolecular or intramolecular.
Another aspect of the invention relates to a method of forming a copper-containing material on a substrate, comprising vaporizing a copper precursor composition to form a precursor vapor, and contacting the precursor vapor with a substrate to form the copper-containing material thereon, wherein the copper precursor composition includes at least one precursor selected from the group consisting of:
(a) precursors of Formula I 
xe2x80x83wherein
M is xc2xd, 1 or 2
Rxe2x80x2 and Rxe2x80x3 are the same or different and are independently selected from the group consisting of C1-C8 acyclic alkyl, aryl, fluoroaryl, C1-C8 fluoroalkyl, C3-C6 cycloalkyl, and C3-C6 fluorocycloalkyl; and
L is a neutral Lewis base ligand, selected from the group consisting of (i) alkenes, (dienes), (ii) alkynes, (iii) silicon containing ligands, and (iv) sulfur, oxygen and/or nitrogen-containing organic ligands;
(b) precursors of Formula II: 
xe2x80x83wherein
R1, R2, R3 R4 and R5 may be the same or different and are independently selected from the group consisting of H, aryl, fluoroaryl, C1-C8 acyclic alkyl, C1-C8 fluoroalkyl, or C3-C6 cycloalkyl, and
n is 0, 1, 2, or 3.
Other aspects and features of the invention will be more fully apparent from the ensuing disclosure and appended claims.